The present invention relates to a method for preparing overbased materials in media which are subject to hydrolysis.
Overbased materials, also referred to as superbased or hyperbased materials, are well known additives in the field of lubrication. These materials are metal salts of acidic organic compounds. Overbased materials are generally single phase, homogeneous, and generally apparently Newtonian systems characterized by a metal content in excess of that which would be present according to the stoichiometry of the metal and the particular acidic organic compound reacted with the metal. overbasing, generally, is a means for supplying a large quantity of basic material in a form which is soluble or dispersible in oil. A variety of media are known which are useful as the oil in which the overbased salt can be dissolved or suspended. Many materials, however, have been practically precluded from use as the medium because they are not stable under the conditions of overbasing. Noteworthy in this regard are esters, including synthetic ester oils and natural ester oil products. The present invention provides a method for preparing overbased materials in such hydrolytically unstable media.
U.S. Pat. No. 3,766,066, McMillen, Oct. 16, 1973, discloses a process for preparing solid, metal-containing micelliar complexes by isolating the solid, metal-containing matter from homogenized, overbased organic acids with the aid of conversion agents. The metal-containing materials can be separated from the diluents by thin-film evaporation techniques, vacuum distillation procedures, precipitation techniques, and the like. The metal containing compositions are readily and stably dispersed in nonpolar organic liquids. The nonpolar organic liquid can be, e.g., benzene, hydrocarbons, halogenated hydrocarbons, such as 1,1,1-trichloroethane. The solids can also be incorporated into various plastics, paints, caulks, rubbers, and the like.
U.S. Pat. No. 5,300,242, Nichols et al., Apr. 5, 1994, equivalent to PCT publication WO93/18119, Sep. 16, 1993, discloses a metal overbased composition comprising at least one natural animal or vegetable oil, a metal base oxide, hydroxide, or alkoxide, to form a saponified intermediate, and reacting excess metal base with an acidic gas. The reaction can be conducted in xylene. During post-reaction vacuum stripping, a vegetable oil can be added as a diluent.
European Publication 405 879, Jan. 2, 1991, discloses preparation of basic calcium sulphonate by carbonating a substantially oil free mixture of a sulphonic acid and or an alkaline earth metal sulphonate, a hydrocarbon solvent, an alcohol, and an excess of calcium oxide or calcium hydroxide, removing the residual alcohol and optionally adding the medium other than oil in which it is desired to obtain the basic calcium sulphonate and removing the hydrocarbon solvent used. A lubricant can be obtained by adding a lubricating medium such as a synthetic ester or fatty acid ester.
U.S. Pat. No. 5,238,276, Best et al., Feb. 1, 1994, discloses coating compositions comprising a dispersion or solution of (a) colloidal size amorphous overbased sulfonate, (b) solvent or plasticizer, and (c) polymeric material soluble in the solvent or compatible with the plasticizer. Preferably the composition is free from any mineral oil. A lubricant may be obtained by adding a lubricating medium such as a synthetic ester or fatty acid ester.